Bms help

[Libertad87]

I just bought 8 battery 280 ah lifepo4 3.2 volt i would like to install in 4s2p.
Can someone draw a practical graph to connect only one bms.t

Tha

 

[FilterGuy]

I just bought 8 battery 280 ah lifepo4 3.2 volt i would like to install in 4s2p.
Can someone draw a practical graph to connect only one bms.t

Tha

4S2P requires two BMSs. To use only one BMS you need 2P4s.

Please review this:

Cell Configurations for 12V 24V and 48V LiFePo4 Batteries

This short deck shows 1P and 2P cell configurations for 12V, 24V & 48V LiFePO4 batteries. To get the deck, click on the orange button at the top of this page. Note: Reviews, Comments and corrections are welcome Document Revision History...

diysolarforum.com

 

[Libertad87]

Is it a good deal? Cell will be fine tune?
Thx

 

[Libertad87]

And sorry .. for balancing before installing can I do with a buck dc converter cuz I don't have ac charger ... Or bms will do everything alone.
Thx

 

[FilterGuy]

There are pros and cons of 2P4S and 4S2P. A lot of folks really want to monitor each cell individually. I don't believe that is necissary so I try to do parallel first where I can. The document I pointed to lays out the trade-offs.

 

[FilterGuy]

And sorry .. for balancing before installing can I do with a buck dc converter cuz I don't have ac charger ... Or bms will do everything alone.
Thx

I would have to know more about the set-up with the buck DC converter.

 

[Acho_303]

I just bought 8 battery 280 ah lifepo4 3.2 volt i would like to install in 4s2p.
Can someone draw a practical graph to connect only one bms.t

Tha

I order my 120amp bms here -
US $7.38 11%OFF | smart 4S cells 12V 120A 1000A Lifepo4 li-ion Lithium battery protection board W balance High Current BMS Bluetooth APP GPRS Modu

8.29US $ |smart 4S cells 12V 120A 1000A Lifepo4 li ion Lithium battery protection board W balance High Current BMS Bluetooth APP GPRS Modu| | - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

a.aliexpress.com

I based my selection on a thread on here with a poll to the bms everyone was using... I basically got two BMS for my 8cell lishens. 24 volt system could be established with one bms

 

[Libertad87]

i am connect to a gel battery that is goind slowly dead.. so i bought the lifepo4 set. i read that i need to balance them before instaling.
they recommend a scientific charger with variable volt current etc.
i dont have that but a step down dc convert can send a 3.2 v constant from my gel battery. or the ac system charger is something different
thansk

 

[FilterGuy]

i dont have that but a step down dc convert can send a 3.2 v constant from my gel battery.

You typically want to top balance to 3.6 or 3.65V.

Edit: Corrected the following link:

Explanation for Beginners of Top and Bottom Balance

To get the document, click on the orange button at the top of the page. This is a beginner's explanation of top and bottom balancing cells that should help you understand what it is all about. NOTE: This is not intended to be a tutorial of how...

diysolarforum.com

Top Balancing LiFePo4 Cells using a low cost benchtop power supply.

To get the paper, click on the orange at the top of this page. This is a tutorial with detailed steps on how I top-balance my LiFePO4 Cells using a low-cost benchtop power supply. To get the tutorial, click on the orange "Download" button...

diysolarforum.com

 

[HRTKD]

My recommendation is that you don't try to do this on the cheap. Use the tools recommended and be sure to employ plenty of patience. Deviating from the tried and true methods can be risky unless you really know what you're doing.

I bought a benchtop power supply and thought for sure that it would be used once only. But I've found other uses for it, so it hasn't been sitting on a shelf. Worst case, sell it on Craig's List. This is the one I bought.

DC Power Supply Variable 30V 10A, 4-Digital LED Display, Precision Adjustable Switching Regulated Multifunctional Power Supply Digital with USB Interface, Disply with Output Power Lab Grade: Amazon.com: Industrial & Scientific

DC Power Supply Variable 30V 10A, 4-Digital LED Display, Precision Adjustable Switching Regulated Multifunctional Power Supply Digital with USB Interface, Disply with Output Power Lab Grade: Amazon.com: Industrial & Scientific

www.amazon.com

 

[FilterGuy]

My recommendation is that you don't try to do this on the cheap. Use the tools recommended and be sure to employ plenty of patience. Deviating from the tried and true methods can be risky unless you really know what you're doing.

I bought a benchtop power supply and thought for sure that it would be used once only. But I've found other uses for it, so it hasn't been sitting on a shelf. Worst case, sell it on Craig's List. This is the one I bought.

DC Power Supply Variable 30V 10A, 4-Digital LED Display, Precision Adjustable Switching Regulated Multifunctional Power Supply Digital with USB Interface, Disply with Output Power Lab Grade: Amazon.com: Industrial & Scientific

DC Power Supply Variable 30V 10A, 4-Digital LED Display, Precision Adjustable Switching Regulated Multifunctional Power Supply Digital with USB Interface, Disply with Output Power Lab Grade: Amazon.com: Industrial & Scientific

www.amazon.com

Back when I first got into this I was the same way.... I did not want to buy a power supply for a single use. After I bought it, I not only do I use it all the time, I ended up buying a second one to use!

 

[Libertad87]

Thanks i order a power supply... I,ll like to know which gage of wire should I use for parallel bridge. Max 100amp
Measure in mm plz

 

[HRTKD]

Thanks i order a power supply... I,ll like to know which gage of wire should I use for parallel bridge. Max 100amp
Measure in mm plz

Parallel bride of what? Please explain what you're trying to do.

 

[Libertad87]

In doing a 2p4s of 280 ah cell. I'll have only 16bus bar.so I'll make other bridge with cable.
Thx

 

[HRTKD]

For a 2p4s configuration, you need 11 bus bars. Unless you're doubling up the bus bars. Then you need double that number. Keep in mind that when you double (quadruple?) the bus bars, you need longer bolts to ensure that enough of the threads are making contact.

To figure out the equivalent size cable, you need to first figure out the amp rating of the bus bars. The cross section of the bus bar is what is used to determine that. Here is a random table I found that can be used for that.

Electrical: Busbar - Table 3: Quick Busbar Selector

Knowing the ampacity, designers and estimators can get the approximate bus bar size. Ampacity of the bus bar selected must then be verified by checking table 1.

www.copper.org

Take the amp rating and plug it into the table below to get the cable cross section.

Current Carrying Capacity Table | Calculate Cable Cross Section

www.sab-cable.com

 

[FilterGuy]

In doing a 2p4s of 280 ah cell. I'll have only 16bus bar.so I'll make other bridge with cable.
Thx

For top balancing 8 cells you need 14 bus bars

If you don't have enough bus bars you can use wire for the remaining connections just fine. The size of the wire depends on the current you will be pushing. If you have a 10A power supply you could get away with some fairly small wire, but i would recommend something like 10AWG.

Note: while you are top balancing you *will* see differences in voltage between the cells. Don't worry about it. The differences are due to voltage drops accross the wires and bus bars. As the cells reach full charge, the current will drop and the voltage drops will go away.

 

[FilterGuy]

In doing a 2p4s of 280 ah cell. I'll have only 16bus bar.so I'll make other bridge with cable.
Thx

I just re-read your post..... are you asking about using wire during top balance or with a 2P4S hook-up?

With a 2P4S set-up, there are a lot of ways to arrange the cells.... some need more bus-bars than others:

There are other arrangements besides what is shown above. How are you planning to arrange them?

Cell Configurations for 12V 24V and 48V LiFePo4 Batteries

This short deck shows 1P and 2P cell configurations for 12V, 24V & 48V LiFePO4 batteries. To get the deck, click on the orange button at the top of this page. Note: Reviews, Comments and corrections are welcome Document Revision History...

diysolarforum.com

 

[Libertad87]

Thanks you every one I'm trying to connect the bms.. maybe i have the wrong one it's a 16 s and i want to connect only 4 s.. it's possible I dont see good voltage reading in the ant bms app. I telling charge mos and discharge mos no cable connect. Help I'm kinda lost

 

[HRTKD]

Some BMS are specific to a voltage. A 16s BMS usually needs 48v, not 12v.

 

[Libertad87]

But in the settings it's write u can change number of balance wire..u te shure i can't build an 4s?